Engine piston



C. Y. KNIGHT.

ENGINE PISTON.

APPLICATION FILED JUNE 12. 1918.

1,41,?19, v PatentedJune 5, 1922,

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cnannns Y. KNIGHT, or PASAD N CAL FORNI ASSIGNOR To THE KNIGHT- AMERICANPATENTS COMPANY, or CHICAGO, ILLINOIS, A CORPORATION OF DE AWARE.

is re.

I ENGINE PIsTON.

Patented June 6, 31922.

. Application filed llune 12,1913. Serial No. 239,500.

To all tohom it may. concern:

Be it known that I, CHARLES Y. KNIGHT, a

citizen of the United States, residing at Pasadena, in the county of LosAn eles and State of California, have invente' certain new and usefulImprovements in Engine Pistons, of which the following is a specification.

This invention relates to pistons for engines of various types andespecially for in ternal combustion engines, andhas for its object theprovision of a device of the class named which shall be of improvedconstruc- ,tion and operation.

The invention is exemplified in the com-. bination and arrangement ofparts shown in the accompanying drawing and described in the followingspecification, and it is more particularly pointed .out in the appendedclaims.

In the drawing- Fig." l is a longitudinal sectional view of an englnepiston of the ordinary trunk type showing my invention applied thereto;and

Fig. 2 is a section of the piston shown in Fig. l.

In engine construction it is well, known that pistons should be desi nedfor li htness, speed, tightness of fit, an silence o operation, and thedifiiculties in securing all 0 these characteristics are well known toenthe effort has been to construct pistons of metal which has thisproperty, such as aluminum, or some aluminum f compound or alloy; but itisv usual to make the cylinder itself of cast ironjsince the cylinderdoesnot reciprocate and does not require the same degree of lightnessasthe moving parts. Where an aluminum piston is used in a cast ironCyllli der it has heretofore been necessary to sacrifiee'some of theother characteristics named above because of thefact that iron and aluminum vary greatly in their coeflicient of expansion, the expansion ofaluminum being much greater under the influence of the heat producedinthe. cylinder than is that of the cylinder itself. For this reason ithas been necessary to allow a very considerable clearance between thealuminum piston and the cylinder walls in order that the piston will notstick when it reaches the temperature it attains under runningconditions. This means that the piston must necessarlly be loose in thecylinder In order to' secure lightness My. invention contemplates anarrangement of parts that shall permit of the construction of the pistonfrom alight metal, such as aluminum, andyet shall so regulate theexpansion of this piston that it shall conform to the expansion of itscooperating cylinder made of a difierent metal. The mam ner in whichthis result is secured will best be understood from a description of theembodiment of the invention illustrated in the drawing, in which thenumeral 1 designates a piston of the ordinary trunk type having theusual piston ring grooves 2 and gudgeon pin 3. The piston may be made ofaluminum 'or a similar light metal and operates in the cylinder 4 ofcast iron, or of whatever metal the manufacturer wishes to use for thispurpose. Just below the gudgeon pin 5 the in terior of the piston 1 isprovided with a, circumferential groove 6 which has a rib 7 adjacent theinner side thereof, and a smaller f iron, or if the cylinder is of someother material, the ring 9 is made of the same .material so that itscoeflicient of expansion shall be the same as that of the cylinder. Thering 9 at ordinary temperatures has anouter di- 4 ameter slightlygreater than the normal inner diameter of the groove 6 in the piston.The ring is forced into position in the groove under heavy pressure sothat the walls of the piston are placed under tension and stretchedoutwardly giving the piston a diameter, adjacent the ring, somewhatgreater than that which it would normally have were the ring omitted. Inorder to facilitate the expansion of the piston under the internal.pressure produced by the ring 9, a series of slits 10 may be cut throughthe piston wall in various spaced positions around its periphery, asshown in the drawing. In place of slits other ineans for weakening thecylinder walls to permit expansion will readily occur to those skilledin the art, or the ring may be forced into place without any suchprovision, reliance being had upon the elasticity of the metal itself topermit the necessary expansion under the pressure of the ring.

WVhen a piston, constructed as described, is subjected to the heatproduced in the engine, the ring 9 will expand at the same rate as thecylinder in which the piston operates, and the expansion of the piston,adjacent the ring, will be controlled by the ring, since the tension inthe walls of the piston will hold these walls tight against the exteriorof the ring, and the more rapid expansion of the metal in the pistonwill merely tend to relieve this tension as the temperature increasesinstead of moving the walls outwardly toward the cylinder. In this waythe piston may be made to fit quite closely to the walls of the cylinderat ordinary temperatures, and since its rate ofexpansion will becontrolled by the ring 9, which expands at the same rate as thecylinder, the fit will continue to be the same for all temperatures towhich the engine is subjected.

I claim 1. In combination, a piston, a cylinder in which said pistonoperates, said piston and cylinder being composed of metals havingdifferent co-efficients of expansion, and a member within said pistonand arranged to exert outward pressure thereon to control the expansionof said piston under changing degrees of temperature.

2. In combination, a cylinder, a piston arranged to operate within saidcylinder, said piston and cylinder being composed of different metals,and a member composed of a metal having a co-efiicient of expansionsimilar to that of said cylinder and fitted within said piston andexerting outward pres sure thereon to control the expansion andcontraction of said piston under changing temperatures within saidcylinder.

3. In combination, an iron cylinder, an aluminum piston arranged tooperate within said cylinder, said piston having an internalcircumferential seat therein, an iron ring fitted under pressure withinsaid seat and having an external diameter suflioient to exert outwardlydirected force on the interior of said piston to hold said piston inexpandcylindrical portion of the piston and retained in position therebyfor expanding only the intermediate cylindrical portion of the piston;

5. An expansible piston comprising a head portion, and a cylindricalportion having a circular groove formed in the inner surface thereof;and a closed ring adapted to be forced into the groove formed in thecylindrical portion of the piston and retained in position thereby forexpanding the cylindrical portion of the piston.

6. An expansible piston comprising a head port-ion and a cylindricalportion, provided with vertical slits, terminating short of the lowerend of the cylindrical portion, a groove formed on the inner surface ofthe cylindrical portion intermediate the ends of the slits, and anendless expanding ring adapted to be forced into the groove and toexpand evenly the slitted portion of the piston.

7. An expansible piston comprising a head portion and a cylindricalportion, said cylindrical portion comprising an upper and lower sectionsof unbroken metal, and a slitted portion intermediate said sections, acircular groove formed in the inner surface of the slitted portion andan annular member forced into the groove and adapted to expand theslitted portion of the cylindrical portion.

In testimony whereof I have signed my name to this specification on this28th day of February, A. D. 1918.

CHARLES Y. KNIGHT.

